Climate change to intensify dengue outbreaks: Experts

NEW DELHI: Dengue has already killed at least 17 people in the capital; hundreds more have contracted it. Experts say this is an example of how climate variability-fluctuations in weather patterns-might accentuate certain disease outbreaks in the future.

Scientists at National Institute of Malaria Research (NIMR) as well as municipal health officials have found a direct link between a long humid season and the span of the disease season. A prolonged monsoon with intermittent rains made it ideal for Aedes aegypti mosquitoes to breed and transmit the virus for a longer time, they said. It has also been seen that the transmission window of dengue is extending over the years.

Along with poor preparedness, it can be disastrous for Delhi, said NIMR scientists. "The rains advanced this year. Delhi had good rain from July to August 24. It was followed by a dry spell and then two wet spells again in September. Such spells may continue till November. Humidity is a key factor in longevity of the mosquito vector. Though El Nino was predicted this year, there was a deviation in its impact and the monsoon was not completely deficient," said R C Dhiman, a scientist at NIMR who specialises in climate change. "In comparison to 2014, the case number is very high this September," he added.

While dengue cases were always reported in December, the numbers used to be small. "In 1997, there were only seven cases, in 2002 about 18, and in 2003 it was about 15. But in the last two years there have been more than a hundred cases in December. Any rise in temperature will ensure that dengue thrives even in colder months," said another scientist.

A C Dhariwal, director, National Vector-Borne Disease Control Programme, said the link between dengue outbreaks and climate change is well documented. "Intermittent rains ensure that they breed again and again. A new virus has a compounding effect on the problem."

But there is hope as an ongoing NIMR study on robust prevention techniques has found positive results. According to this study, which will be published in the WHO bulletin in the next few months, dengue mosquitoes breed almost round the year in Delhi in overhead and curing tanks, and plastic containers in homes. "This was based on three to four years of research all over Delhi. We applied this finding to 20 locations in the west zone. About 200 households were chosen in each locality and all the breeding containers were cleared before the monsoon. These houses did not report a single dengue case thereafter," said B N Nagpal, a scientist at NIMR.

Unplanned urbanization and shortage of water in the city could be behind fuelling such outbreaks. "People are storing tanker water because there is a shortage. Most overhead tanks are not accessible for cleaning," he said. Almost every house surveyed has 15-16 containers like flower vases, and Feng Shui, bamboo and bird feeding pots conducive for mosquito breeding, Nagpal added.

Only in India the healthcare financing is very small when compared to the financing by the other forces rather than the patient himself or herself paying out of pocket. Having 70-75% of the expenses as out-of-pocket, in my opinion, is not a right approach to managing healthcare in a country where the patients tend to sub-optimally purchase healthcare if he/she has to pay out-of-pocket.